Since the thread has detoured towards calling a General Election:
https://en.wikipedia.org/wiki/Snap_election
Generally speaking, the Prime Minister under such systems does not have the legal power to call an election, but rather must request the election be called by the head of state. In most countries, the head of state always grants such a request by convention.
The conditions for when a snap election can be called have been significantly restricted by the Fixed-term Parliaments Act 2011 to occasions when the government loses a confidence motion or when a 2/3 majority of MPs vote in favour.
http://www.independent.co.uk/news/uk/politics/early-general-election-can-theresa-may-actually-call-one-a7132846.html
No, there are two ways under the FTPA that an election can be called ahead of schedule.
The first is if two thirds of MPs vote to hold an election. This is a very high bar and would in practice require both Labour and Conservative support.
The second is if there is a no confidence vote in the government of the day. After such a vote other parties are given 14 days to form another government. If none can be formed, a new election is held.
On paper, a majority government could, by a simple vote, declare “no confidence” in itself. Since no other party has a majority, after 14 days an election would be set.
Seems to me that May could effectively call one, but, even though Labour is presently in disarray, there's no guarantee the Conservatives would strengthen their position by calling one. They could end up with a drop in MPs and a coalition government.